Coin-operated apparatus are being increasingly used throughout the world to provide goods and services. Such apparatus includes amusement machines, vending machines for a wide variety of products, gaming machines (such as "poker machines") and payphones.
As a sub-group, vending machines dispensing such varied products as public transport tickets, confectionery, video cassettes and breadsticks are increasingly apparent in developed countries due to the high cost of labour and a demand for twenty-four-hour access to such products.
In addition, public telephones or payphones are becoming more sophisticated. Although there is a trend towards payphones which operate only on a "phone card" or credit card, it is likely that future payphones will be modelled on those currently in use in Italy, in which one may use coins, phone cards or gettoni (telephone tokens).
Although there are in use banknote validators, the problems inherent in "reading" banknotes (particularly mutilated or worn banknotes) coupled with the trend in most countries to replace lower denomination banknotes with coins, means that in all of the abovementioned applications, a coin validator will be required.
To be acceptable in one of the abovementioned applications, a coin validator must quickly and accurately discriminate between coins of different values, between coins of different countries and between genuine coins and bogus coins. Existing coin validators have been unable to discriminate adequately, in some cases, between a low value coin of a foreign country and a higher-value coin of the country in which the validator is located. Particularly in a region such as Europe, coin validators additionally cannot cope with the large number of migratory coins from various European countries.
One example of a prior art coin validator is provided by U.S. Pat. No. A-3,918,565, which discloses coin selection methods and apparatus in which data representative of a coin is compared with data store in a programmable memory.
In U.S. Pat. No. A-3,918,565, a numerical value of a signal produced by interrogating a coin, such as frequency, is compared with acceptable numerical values for genuine coins which are stored in the programmable memory.
Another prior art coin validator is disclosed in AU-B-24242/84, which discloses the use of pulsing coils which induce eddy currents in a coin. Monitoring means is used to monitor the decay of the eddy currents, and a comparison between the output of the monitoring means and stored reference values enable discrimination to take place.
It is considered that the approach of AU-B-24242/84 is unnecessarily complicated, and would not permit an adequately rapid discrimination to take place.